Spiral thermostatic switch



Jan. 31, 1950 w. ORVEDAHL SPIRAL THERMOSTATIC SWITCH Filed March 11, 1948 1.5 *60 crew T 70 AC "Qfi Jrezxewfar I Zia fer drveda/z! Jiiarzeeys Patented Jan. 31, 1950 Walter Orvedahl santa Fe, Mex, assignor to Control Devices, Inc., sent-are, Nr'Mexi, a cor- [poratio'n ofNew Mexico I Application March 11, iais; sns ;1 4;zs1

I invention relates to improvementsinl'thermostats and has for one object to provideasimple, cheap, convenient thermostat which may *Pbe used to control the operation ofa houselheate ingor other heating installation, r a

I illustrate my invention as appliedto -the control of an electric motor which ,may be used insconnectionwith any suitable type of house heating apparatus, the motor by means forming no part of mypresent invention-controlling the heat generated by the apparatus and heating the areas in which the thermostat islocated,

My invention is illustrated more'or less diagrammatically in the accompanying drawings;-

wherein: I Figure 1 is a side elevation of the device; Figure 2 is a section along, the lineI 2,- 2 of Figure 1 looking in the direction of thearrows; Figure 3 is a section along the line 3 -3 of Figure 1 looking in thedirect ion of the arrows.

Like parts are indicated by like characters in the drawings.

I, 2 represent the terminals of 110 volts, 60 cycle alternating current supply line. 3 is a motor field coil. 4 is a series condenser. An alternating current circuit is thus established from terminal I through conductor 5, motor field coil 3, conductor 6, condenser 4, conductor 1 back to terminal 2.

I propose to control motor operation by placing in parallel with the field coil 3 a variable resistance 8. This variable resistance is connected to the conductor 5 by a conductor 9 and has a plurality of taps H), II, 12, I3 and I4. These taps are connected by conductors l5, l5, l1, l8 and I9 respectively to a series of contact buttons 20, 2|, 22, 23, 24, all these buttons being supported in insulating panel 25. Projecting forwardly from this insulating panel is a supporting bracket 26 which carries a bi-metal heat sensitive strip 21 rigidly mounted thereon in front of the panel. The conductor 28 extends from the conductor 6 to the bi-metal element 21 thus being in parallel with the motor winding 3.

Carried adjustably on the bi-metal element 21 is a screw 29 which in turn carries a spiral metal strip 30. Plan view in Figure 2 shows the relationship between the spiral contact strip 36 and the contact buttons 20 to 24 inclusive. It will be noted that these contact buttons are arranged in a spiral on the supporting plate B conforming generally to the outer coils of the spiral contact member 30. The spiral member 30 is so spaced and positioned that when pressure is applied to force'the contact member "againstthebuttons 20 to 24 inclusive, the spiral -.collapses gradually, button 20 being "first con- -tacted by. the spiral then'button 2|, next 22, 23, 2,4intheirsequence. s ,;-,.,ltisnecessary, of course, thatthemetal of the spiral strip 30 besufliciently elastic and its yvcrtical -pitch of .thespiral sufficiently low so that the spiral will always recover its original form after having been pressed until all, or at least those turns which engag the buttons, have the" ambient temperature of a room in which {th thermostat is located, and the room is to be i5ccupiedacommon'plane.

Assuming thatjthe element 21 is exposed to "(heated by a heaterfincludingthe motor whose field coil is illustrated in 3 with the parts in the position. shown in Figure .1, there is a contact between the c'oil 30,fthe,contaot button, so

that'the entire resistor 8 is in parallel with the field coil 3. Under these circumstances but little, if any, current passes through the resistor, the total resistance being greater than th resistance of the field coil 3.

As the temperature increases, the arm 21 moves to the right until contact button 2| is engaged by the coil at which time part of the resistance is removed from the circuit. Further tem erature increase moves the arm 21 further to the right and contact button 22 and so on, puts out additional increment of resistor 8 until contact button 24 is engaged by the spiral element 30, the resistance of the resistor 8 has dropped to a minimum.

Each time the resistance is decreased, more current tends to pass through the resistor and less through the coil 3 so that increased temperature causes the spiral to move toward the contact to decrease resistance although the motor thereby reduces the output of the heater.

It will be noted that decrease in temperature will cause a reverse action but only one of the contact buttons is contacted or disconnected at a time. There is no simultaneous opening or closing of a circuit and so in consistence with the movement of the bi-metal arm as the ambient temperature changes greater or less resistance is inserted in the circuit in parallel with the motor field coil so that as temperature rises motor speed and power decreases, as temperature falls motor speed and power increases.

The contact members 20 to 24 inclusive are threaded in the insulating block 25 as indicated at 40 in order that the extension of the contact members toward the base of the strip may be and from the contact members independent of the position of the thermostatic element or plate" 27. This adjustment is,of course, essential in setting the annular start and end point ofthe cycle, but it is essential also that such adjust ment impart no rotational or angular movement of the spiral with respect to the electric contact members, as otherwise the members might be' moved out of registerwith that part of the strip which it is intended they will contact.

For convenience I have shown the conical strip mounted on the bi-metal thermostat element. Obviously the member 25 might be the movable member and 21 might be fixed, or both might be movab1e,'or other temperature responsive means might be used to change the relative position of the coil and the associated contact members. 3

I claim:

1. In combination, a temperature responsive thermostatic element, a metal conductor strip wound to form a conical spiral, and supported at its apex on the thermostatic element, a series v of, insulated electrical contact members, spirally arranged, in register with the convolutions of the strip, adjacent the base thereof, and so positioned that as the strip is moved by the thermostatic element toward the contact members the strip collapses axially to contact successive contact members.

2. In combination, a temperature responsive thermostatic element, a metal conductor strip wound to form a conical spiral, and supported at its apex on the thermostatic element, a series of insulated electrical contact members, spirally arranged, in register with the convolutions of the strip; adjacent the base thereof, and so positioned that as the strip is moved by the thermostatic element toward the contact members the strip collapses axially to contact successive contact members, means for adjusting the strip with respect to thermostatic element toward and from the contact members.

33111 combination, a temperature responsive thermostatic element, a metal conductor strip woundto form a conical spiral, and supported at its apex on the thermostatic element, a series of insulated electrical contact members, spirally arranged, in register with the convolutions of the strip, adjacent the base thereof, and so positioned that as the strip is moved by the thermostatic element toward the contact members the strip collapses axially to contact successive contact members, and means for preventing angular movement of the conductor strip about the 'axls of the conical spiral. WALTER ORVEDAHL.

REFERENCES CITED The following references are of record in the file oi this patent:

UNITED STATES PATENTS 

